Electric-fuse link.



INVENToR.

Patented Aug. 27, l1918.

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R. C. COLE. ELECTRIC FUSE LINKI APPLICATION FILED MAR. 28. 1918.

A TTORNE Y.

UNITED STATES PATENT OFFICE.

ROBERT C. COLE, OF HARTFORD, CONNECTICUT, ASSIGNOR T0 THE JOHNS-PRATTCOM- PANY, OF HARTFORD, CONNECTICUT, A CORPORATION 0F CONNECTICUT.

ELECTRIC-FUSE LINK.

Patented Aug. 27, 191s.

Application filed March 28, 1918. Serial No. 225,178.

To all whom t 'may concern:

Be it known that I, ROBERT C. COLE, a citizen of the United States,residing at Hartford, in the county of Hartford and State ofConnecticut, have invented a new and useful Improvement in Electric-FuseLinks, of which the following is a specification.

This invention relates to the construction of the fuse links of inclosedelectric fuses.

The object of the invention is to provide a simple, cheaply formed andaccurately calibrated link which will indefinitely carry a normal amountof current withoutl undue heating, and which will either in a filled orin an unfilled case under gradual-overload or severe short circuitconditions open the circuit in which it is placed with less explosiveeffect and more quietly than the links in common use.

This object is attained byarranging calibrating perforations in suchmanner that there will be in the link a plurality of attenuated sectionsor constricted current paths in multiple, and a plurality of thesemultiple attenuations or constrictions in series whereby when anabnormal current flows there will' be but small sections of metal tomelt and these will be so distributed that there will be a number ofarcs in multiple-series of relatively small size, consequentlysuflicient internal pressure is quickly built up to compress andextinguish the arcs before they become violently destructive andpressure enough is generated to burst the tube or blow off the end caps.

Links which embody this invention have distinct advantages in filledfuses, but they are particularly serviceable for use in unfilledrenewable fuses, and consequently they are illustrated herein as used inthe latter fuses.

Figure 1 of the accompanying drawings shows a central 4longitudinalsection of an inclosed fuse of the ferrule' Contact type provided with alink constructed according to this invention. Fig. 2 shows the linkremoved from the case of this fuse. Fig.- 3 shows a link ofsubstantially the same carrying capacity constructed for a highervoltage fuse. Fig. 4: shows a central longitudinal section of aninclosed fuse of the knife blade contact. type, provided with a linkVwhich embodies this invention. Fig. 5 shows the link removed from theknife blade fuse. Fig. 6 shows a link for a knife blade fuse of highervoltage.

The case 1 of these fuses is usually formed `of a piece of fiber tubing.On the ends of the tubular case shown in Fig. 1 metallic sleeves 2 arethreaded, and screwing upon the outer ends of these sleeves are metalliccaps 3. In the ends of the sleeves and resting on ,shoulders thereinbent over these washers and clamped thereto by the caps are the endsvofthe fusible link 5.- These links are usually formed of thin zinc strips.In the form first illustrated two triangular perforations 6 are madethrough the strip on each side of the middle. This results in forming onone side of the middle of the strip two attenuated sections 7 8, nearthe edges and an attenuated section 9 along the center of the strip, andforming on the other side of the middle two attenuated sections 10,11,near the edges and an attenuated section 12 along the center of thestrip. This strip, which has the desired current carrying capacity andwith the calibration perforations properly spaced apart according to thevoltage, thus has three constricted current carrying paths 7 8, 9, inmultiple, and in series therewith three constricted current carryingpaths 10, 11, 12, which are in multiple with each other. Between theseattenuated sections there is a sufficient mass of metal to are washers 4and provide the required current carrying ca'- pacity and proper heatradiation for insuring the desired result. /The attenuated sections,however, are so small that when an abnormal current flows the metalmelts quickly where the current paths are constricted, and as theseportions melt three small arcs are formed in multiple at one side o themiddle and threesmall arcs in multiple are formed at the other side ofthe middle. As the result of the small amount of metal that is necessaryto be melted and the d1- viding of the currentl `in this manner theseveral arcs are relatively small and they are smothered by the internalpressure before they become sufficiently7 large to become eXplosively,violent For a relatively low voltage fuse there need be but two sets ofcalibration perforations providing three'constricted multiplecurrentpaths in series with three other constricted multiple-current paths. Forfuses of higher voltage more calibration openings may be arranged, asshown in Fig. 3. In this form there are four series of three attenuatedsections arranged in multiple.

The knife-blade type of fuse shown in Fig. 4 has an insulating tubularcase 13 With end caps 14 screwed thereon. Extending through the end capsand through Washers In these links there may kbe as many of these setsof calibrations providing multiple attenuated sections arranged inseries asthe voltage may require for the successful op eration of thefuse, and these calibration perforations may vary 1n size and outllneaccording to the conditions.

This construction provides a sufficient amount of-metal in the strips toinsure the necessary radiation to keep the stripsl cool when in useunder normal conditions,' and yet the sections' of metal necessary to bemelted for opening the circuit are so small that they melt easily andWitlout generating an excess of pressure in the cases and as the currentis broken up into a number of arcs When these small sections melt thearcs are not sufficiently powerful to become violently destructive andthey are easily smothered -by a relatively lo'W pressure generated inthe metal having sets of Calibrating perforations located to provide inseries with each other a plurality of constricted current carryingIsections that are in multiple with each other.

2. A fuse link formed of a strip of fusible I metal having a pluralityof Calibrating perforations arranged in pairs.

3. A fuse link formed of a strip of fusible metal having Calibratingperforations located to provide in series a-plurality of restrictedcurrent carrying paths that are in multiple.

4. A fuse link formed of a strip of fusible metall having Calibrating'perforations located to provide a number in series of three constrictedcurrent carrying paths that are in multiple.

5. Av fuse link formed of a strip of fusible metal having a plurality ofpairs of triangularly shaped Calibrating perforations.

6. A fuse link formed of a strip of fusible metal having Calibratingperforations located to form three constricted current carrying paths ata number of points along the length of the strip.

7 A fuse link formed of a strip of fusible metal having a pair oftriangularly shaped Calibrating perforations located base to base eachside of the middle of the length of the strip.

ROBERT C. COLE.

